1. Field of the Invention
This invention relates to an electrical terminal having an insulation displacement contact section reinforced with a back-up spring.
2. Description of the Prior Art
Insulation displacement contacts (IDC) are increasingly common in the electrical industry because they allow simultaneous termination of a plurality of terminals to respective conducting wires in a simple automated procedure whereby the wires do not need to be stripped and are simply forced into IDC slots with a stuffer tool. There is a rapidly rising demand, particularly in the automobile industry, for electrical terminals that can be assembled in an automated procedure, whilst the electrical current carrying capability, reliability, compactness and robustness are also subject to challenging requirements.
Some of the important factors determining the current carrying capability of a terminal is the conductivity of the metal from which the contact is formed, and the contact resistance between mating terminals or between the conducting wire and terminal. The latter is largely determined by the contact pressure exerted therebetween which in turn is determined by the spring forces that engage the contact surfaces together. Unfortunately, the sheet metal commonly used for producing electrical terminals usually decreases in resiliency as the conductivity and ductility increases. Additionally, there is also an increase in the creep properties i.e. stress relaxation of the material over time and as a function of temperature and stress. The latter is aggravated by the requirement to produce compact terminals having small material cross-sections engendering high resistance and therefore high temperatures during the passage of electrical current, whereby the high temperatures greatly increase the rate of creep of the metal.
It is known in the prior art to increase the contact pressure between mating terminals by providing a back-up spring made of a resilient temperature resistant material such as steel, that provides added resilient forces stable over time and at operating temperatures. One of the problems with some of these terminals with back-up springs, is that the back-up spring only participates in providing the overall contact pressure, whereby the contact body itself provides the remaining force and the contact material must therefore be sufficiently resilient which in turn decreases the conductive properties thereof. In the prior art, sufficient resiliency of the contact material is also required to provide a suitable connection between the IDC slots and the conducting wire connected thereto, in order to ensure that the contact pressure therebetween does not relax due to creep.